One approach to measuring and evaluating different antenna coefficient combinations with multiple receive antennas is to route the outputs of the multiple receive antennas to different combining filters. One filter can be set to the set of antenna coefficients being used for current downlink signal processing, and that filter's output can be routed to the input of a 1st RF processing chain in the receiver. A second filter can be set to a second set of antenna coefficients, e.g., a set of test coefficients, and the second filter's output can be input to a 2nd RF processing chain in the receiver. Received signals are processed by each chain, channel quality in terms of signal to noise ratio (SNR) is measured for each chain and the results are stored. Subsequently, the set of test coefficients for the second filter are changed to another set of test coefficients and the channel quality measurement is again performed. After a sufficient number of sets of test coefficients have been evaluated, a comparison is performed and the set of coefficients providing the best channel quality is loaded into the 1st filter. This approach has the disadvantages that two filters and two RF receiver chains are required, which increases cost, size, weight, and power consumption. In addition, the testing between different potential test coefficient sets is rather slow for each channel quality measurement. Based on the above discussion there is a need for improved methods and apparatus to measure and evaluate different antenna coefficient combining parameter sets.
It would be advantageous if methods and apparatus were developed which allowed for the evaluation of different antenna coefficient combinations using a single RF receiver chain thereby reducing cost and/or power consumption. It would also be beneficial if such methods and apparatus provided for rapid evaluation of test coefficient sets. Measurement techniques that rapidly achieved signal to interference ratio (SIR) information in addition to SNR information would be beneficial in obtaining a better overall selection of antenna combining coefficients.
Since a low cost mobile wireless combination devices with multiple antenna used in combination may be structured to use the same antenna combination simultaneously as a transmit antenna and receive antenna, inventive methods and apparatus that allow for the evaluation of different downlink channels without disrupting the uplink communications from the wireless terminal to the base station would also be beneficial.
A communications system employing some wireless communications devices with multiple antennas used in combination, typically includes many wireless communication devices with only a single antenna. It would be beneficial if the methods and apparatus employed for the wireless communication devices with multiple antennas used in combination did not require the base station to have to distinguish between types of wireless communication devices.